Advances in understanding the pathogenesis of pneumococcal otitis media

Optical Identification of Middle Ear Infection

Ear infection is one of the most commonly occurring inflammation diseases in the world, especially for children. Almost every child encounters at least one episode of ear infection before he/she reaches the age of seven. The typical treatment currently followed by physicians is visual inspection and antibiotic prescription. In most cases, a lack of improper treatment results in severe bacterial infection. Therefore, it is necessary to design and explore advanced practices for effective diagnosis. In this review paper, we present the various types of ear infection and the related pathogens responsible for middle ear infection. We outline the conventional techniques along with clinical trials using those techniques to detect ear infections. Further, we highlight the need for emerging techniques to reduce ear infection complications. Finally, we emphasize the utility of Raman spectroscopy as a prospective non-invasive technique for the identification of middle ear infection.

Cell Invasion and Pyruvate Oxidase-Derived H2O2 Are Critical for Streptococcus pneumoniae-Mediated Cardiomyocyte Killing

Streptococcus pneumoniae (the pneumococcus) is the leading cause of community-acquired pneumonia and is now recognized to be a direct contributor to adverse acute cardiac events. During invasive pneumococcal disease, S. pneumoniae can gain access to the myocardium, kill cardiomyocytes, and form bacterium-filled "microlesions" causing considerable acute and long-lasting cardiac damage. While the molecular mechanisms responsible for bacterial translocation into the heart have been elucidated, the initial interactions of heart-invaded S. pneumoniae with cardiomyocytes remain unclear. In this study, we used a model of low multiplicity of S. pneumoniae infection with HL-1 mouse cardiomyocytes to investigate these early events. Using adhesion/invasion assays and immunofluorescent and transmission electron microscopy, we showed that S. pneumoniae rapidly adhered to and invaded cardiomyocytes. What is more, pneumococci existed as intravacuolar bacteria or escaped into the cytoplasm. Pulse-chase assays with BrdU confirmed intracellular replication of pneumococci within HL-1 cells. Using endocytosis inhibitors, bacterial isogenic mutants, and neutralizing antibodies against host proteins recognized by S. pneumoniae adhesins, we showed that S. pneumoniae uptake by cardiomyocytes is not through the well-studied canonical interactions identified for vascular endothelial cells. Indeed, S. pneumoniae invasion of HL-1 cells occurred through clathrin-mediated endocytosis (CME) and independently of choline binding protein A (CbpA)/laminin receptor, CbpA/polymeric immunoglobulin receptor, or cell wall phosphorylcholine/platelet-activating factor receptor. Subsequently, we determined that pneumolysin and streptococcal pyruvate oxidase-derived H₂O₂ production were required for cardiomyocyte killing. Finally, we showed that this cytotoxicity could be abrogated using CME inhibitors or antioxidants, attesting to intracellular replication of S. pneumoniae as a key first step in pneumococcal pathogenesis within the heart.

Anatomical site-specific contributions of pneumococcal virulence determinants

Streptococcus pneumoniae is an opportunistic pathogen globally associated with significant morbidity and mortality. It is capable of causing a wide range of diseases including sinusitis, conjunctivitis, otitis media, pneumonia, bacteraemia, sepsis, and meningitis. While its capsular polysaccharide is indispensible for invasive disease, and opsonising antibodies against the capsule are the basis for the current vaccines, a long history of biomedical research indicates that other components of this Gram-positive bacterium are also critical for virulence. Herein we review the contribution of pneumococcal virulence determinants to survival and persistence in the context of distinct anatomical sites. We discuss how these determinants allow the pneumococcus to evade mucociliary clearance during colonisation, establish lower respiratory tract infection, resist complement deposition and opsonophagocytosis in the bloodstream, and invade secondary tissues such as the central nervous system leading to meningitis. We do so in a manner that highlights both the critical role of the capsular polysaccharide and the accompanying and necessary protein determinants. Understanding the complex interplay between host and pathogen is necessary to find new ways to prevent pneumococcal infection. This review is an attempt to do so with consideration for the latest research findings.

Cocolonization of Pneumococcal Serotypes in Healthy Children Attending Day Care Centers: Molecular Versus Conventional Methods

OBJECTIVES

Pneumococci are common colonizer, especially of children, and cocolonization of different serotypes is an important factor for intraspecies genetic exchange. The aim of this study was to analyze pneumococcal carriage and serotype distribution in unvaccinated healthy children in Iceland and compare conventional culture methods and molecular methods using DNA extracted directly from the samples.

METHODS

Nasopharyngeal swabs were obtained from 514 children aged 2-6 year attending day care centers in Reykjavik in 2009. The swabs were selectively cultured for pneumococci and the isolates serotyped using latex agglutination. DNA was also extracted directly from the swabs and serotyped using a multiplex PCR panel designed to detect vaccine serotypes and the most commonly carried non-vaccine serotypes.

RESULT

Pneumococcal carriage was detected in 391 (76.1%) of the children using polymerase chain reaction (PCR) and in 371 (72.2%) using conventional methods. Cocolonization was detected in 92 (23.5%) of the carriers when PCR method was used and in 30 (8.1%) when conventional methods were used, detecting 500 and 401 strains, respectively (P < 0.0001). The most common serotypes were 23F, 19A, 6B, 6A and 19F, rates 13-8%. The number of isolates of serotypes included in the 10-valent and 13-valent vaccines and detected by PCR were 234 (58.4%) and 363 (90.5%), respectively and by conventional methods 186 (46.4%) and 293 (73.1%), respectively.

CONCLUSION

Cocolonization was detected in a fourth of the children carrying pneumococci using DNA extracted directly from nasopharyngeal swabs. The rate of carriage was very high, but no serotype dominated, and the children were commonly colonized by vaccine serotypes, especially cocolonized children.

Otitis media associated with Cryptosporidium baileyi in a Saker falcon (Falco cherrug)

A 7-week-old male Saker falcon died with a history of severe refractory dyspnoea and respiratory signs. Microscopical lesions included moderate to severe lymphoplasmacytic inflammation of the middle ears, conjunctivae, third eyelids, choanae, salivary glands of the tongue, turbinates, larynx, trachea, syrinx and bronchi. The lesions were associated with variable numbers of Cryptosporidium spp., further confirmed by transmission electron microscopy and in-situ hybridization. Cryptosporidium baileyi was identified by DNA sequence analysis. C. baileyi may therefore be a cause of otitis media in raptors as it is in man. It is most likely that the middle ears of the Saker falcon acquired the infection through the eustachian tubes that originate near the pharynx in the oral cavity. This is the first description of otitis media associated with C. baileyi in a bird or a mammal except man.

In VitroStreptococcus pneumoniae Biofilm Formation and In Vivo Middle Ear Mucosal Biofilm in a Rat Model of Acute Otitis Induced by S. pneumoniae

Objectives

Streptococcus pneumoniae is one of the most common pathogens of otitis media (OM) that exists in biofilm, which enhances the resistance of bacteria against antibiotic killing and diagnosis, compared to the free-floating (planktonic) form. This study evaluated biofilm formation by S. pneumoniae on an abiotic surface and in the middle ear cavity in a rat model of OM.

Methods

In vitro biofilm formation was evaluated by inoculation of a 1:100 diluted S. pneumoniae cell suspension in a 96-well microplate. Adherent cells were quantified spectrophotometrically following staining with crystal violet by measurement of optical density at 570 nm. The ultrastructure of pneumococcal biofilm was assessed by scanning electron microscopy (SEM). For in vitro biofilm study, S. pneumoniae cell suspensions containing 1×10⁷ colony forming units were injected through transtympanic membrane into the middle ear cavity of Sprague Dawley rats. The ultrastructure of middle ear mucus was observed by SEM 1 and 2 weeks post-inoculation.

Results

The in vitro study revealed robust biofilm formation by S. pneumoniae after 12-18 hours of incubation in high glucose medium, independent of exogenously supplied competence stimulating peptide and medium replacement. Adherent cells formed three-dimensional structures approximately 20-30 µm thick. The in vivo study revealed that ciliated epithelium was relatively resistant to biofilm formation and that biofilm formation occurred mainly on non-ciliated epithelium of the middle ear cavity. One week after inoculation, biofilm formation was high in 50% of the treated rats and low in 25% of the rats. After 2 weeks, biofilm formation was high and low in 25% and 37.5% of rats, respectively.

Conclusion

The results imply that glucose level is important for the S. pneumoniae biofilm formation and S. pneumoniae biofilm formation may play important role in the pathophysiology of OM.

Biofilms and chronic otitis media: an initial exploration into the role of biofilms in the pathogenesis of chronic otitis media

PURPOSE

The aim of the study was to compare the extent of biofilm infection in percentage of mucosal surface area of adenoids removed from children with otitis media with effusion (OME) vs those with recurrent acute otitis media (RAOM) and obstructive sleep apnea (OSA).

MATERIALS AND METHODS

Comparative microanatomical investigation of adenoid mucosa using scanning electron microscopy obtained from 30 children with OME, RAOM, and OSA was used in this study. Seventeen males and 13 females ranging in age from 9 months to 10 years were included in this study. Percentage of biofilm surface area involvement was the main measure.

RESULTS

Adenoids removed from patients with OME had moderately dense mature biofilms covering the mucosal surface with a mean of 27.7% of their mucosal surface covered with mature biofilms. These results were distinct from results obtained from patients diagnosed with RAOM and OSA with means of 97.6% and 0.10% of their mucosal surfaces covered with mature biofilms, respectively. These differences were statistically significant at P < .0001.

CONCLUSIONS

Adenoids removed from patients with OME were characterized by distinctly different percentage of biofilm mucosal surface area coverage, with significantly more biofilm presence than OSA patients but significantly less biofilm presence than RAOM patients. Although previous investigations have supported a dominant role of nasopharyngeal biofilms in RAOM pathogenesis, these results suggest nasopharyngeal biofilms may play a different role in the pathogenesis of OME and that this clinical entity may be more multifactorial in nature.